GROUP OF SPORE-BEARING ANAEROBES 363 



animal is carefully opened, and cultures made from the heart 

 blood in dextrose broth, covered by neutral paraffin oil. In 

 from eight to twenty-four hours the culture tubes show a marked 

 cloudiness, abundant gas-production, and, in most instances, an 

 odor of butyric acid." 



The colonies upon agar and gelatin plates are round, grayish, 

 semitranslucent; the}' are usually nucleated, and resemble those 

 of B. tetani. Upon agar slants a thin, coalescent, yellowish-white 

 growth occurs. Gelatin may or ma}' not be slowly liquefied. 

 Bouillon is clouded with a "heavy precipitate. Little or no growth 

 occurs on potato. Upon blood-serum the growth resembles that 

 upon agar. There is some liquefaction along the line of inoculation. 

 Milk is quickly coagulated, with gas- and acid-production. 

 . Physiology. Growth occurs best at 37. The thermal death- 

 point for non-sporulating culture is 50 for ten minutes, for spores 

 100 for fifteen minutes. Gas is produced from dextrose, lactose, 

 and saccharose, but not from mannite. Probably some differences 

 are to be found in various strains. Gas is likewise produced from 

 pure proteins, such as recrystallized egg-white. The gas formula 



TT 9^ 



is approximately ^Q = -. . Butyric, lactic, and acetic acids 



have been detected. 



Pathogenesis. Experimental Evidence. Intravenous injection 

 of the rabbit frequently, though not always, causes death, but 

 subcutaneous inoculations are without effect. Guinea-pigs are 

 susceptible, as are also pigeons. 



Character of Disease and Lesions Produced. Infections with 

 B. welchii among the lower animals have been noted in few in- 

 stances only, and then only in the rabbit and in the dog, as a result 

 of severe injuries. However, it may quickly invade tissues after 

 death, and give opportunity for mistaken diagnosis. It has not 

 been shown satisfactorily that it ever invades the tissues general!}' 

 before death. It is a secondary invader in practically every in- 

 stance of natural infection. It has been found in emphysema of 

 many organs in the human body. Herter believes that the pres- 

 ence of large numbers of this organism or its varieties in the in- 

 testines is responsible for the production of primary pernicious 

 anemia, particularly in children. 



